1. Los Angeles Air Quality
During hot months, Los Angeles occasionally suffers from temperature inversion
Under normal conditions the air cools with distance from earth’s surface
Emissions normally dissipates into the atmosphere, rising through progressively cooler air

2. Temperature Inversion
Sometimes layer of cooler air from ocean slides under layer of warmer air
Under these conditions, polluted air trapped by layer warm air
Instead of spreading upward, polluted air spreads laterally

3. Temperature Inversion
Ocean breeze doesn’t allow westward expansion
San Gabriel Mountains trap air; causing pollution accumulate in foothills
Most famous case of temperature inversion is the 1952 Great Smog in London

5. Year LA County population 1910 504,131 1930 2,208,492 1950 4,151,687
LA’s air quality began to decline as its population grew
Year
LA County population
1910
504,131
1930
2,208,492
1950
4,151,687
1970
7,041,980
2010
9,818,605

6. Problems of smog became prominent in 1940’s
Episodes occurred in which people suffered stinging eyes and runny noses; visibility also decreased (illustration)
Los Angeles County Air Pollution Control District created through state legislation in 1947

7. In 1967, the state created the Air Resources Board
Agency attacked stationary sources believed to be primary cause of problem. For example:
banned backyard garbage incinerators
mandated emission controls for area steel and iron mills
In 1967, the state created the Air Resources Board
The regional air quality district SCAQMD covering the counties in Los Angeles metropolitan areas created in 1975

8. The source of LA’s primary air quality problem was discovered in late 1940’s
Ozone, a gas found in the upper atmosphere, was forming near ground level
Ground level ozone is more likely to form on hot days that experience temperature inversion

9. Research showed most of the emissions producing ozone came from car exhaust
Auto companies reluctant to develop emissions reduction technology
Over the years, the state of California grew to confront auto industry

10. In mid-1960’s auto industry began equipping cars with emissions control gear
Over 15 years after science indicated cars were the problem

11. What was the reason for reluctance of the industry?
Clean air is public good
Market incentives are not strong to produce the good
Market incentives to alter other aspects of autos much stronger

12. Other proposed solutions
Would high gasoline taxes have addressed problem?
Geography of tax
Support for tax
Public Transportation?
in mid-1950’s there were 7.1 persons for every vehicle in the city of New York, 2.8 persons per vehicle in Los Angeles
Hoy No Circula policy of Mexico City?

13. Alert Ozone Level First Stage 0.5ppm Second Stage 1 ppm Third Stage
In 1955 LA county developed world’s first pollution alert system
Developed system of air monitoring
Alert
Ozone Level
First Stage
0.5ppm
Second Stage
1 ppm
Third Stage
1.5 ppm

14. Ozone level at first stage would today be considered an extreme health hazard
Today, the federal standard in which adverse health effects is estimated to begin is 0.07 ppm average over an 8 hour period

15. 15 first stage alerts in 1955
10 in 1956
Highest recorded ozone in history in LA area was 0.68 ppm in 1955
Last time ozone recorded over 0.50 ppm in LA area was in 1974

16. Alert Ozone Level Health Advisory 0.15 ppm Stage 1 0.20 ppm Stage 2
In 1970’s, statewide alert standard adopted
Ozone ppm levels averaged over 1 hour
Alert
Ozone Level
Health Advisory
0.15 ppm
Stage 1
0.20 ppm
Stage 2
0.35 ppm
Stage 3
0.50 ppm

17. Over the years, air quality in LA has dramatically improved; mainly due to auto emissions technology
Although area still has worst air quality in the country

18. Smog Alert Data AQI Current Los Angeles Air Quality Los Angeles Area Air Quality Historical Air Quality Data